Help files exist in two forms: (i) the source form, which you create using a text editor, and (ii) the library form, which is read by the application program when it calls the HLP_HELP subprogram. The source form is read sequentially (a two-pass operation) by the HLP_CREH routine to write the randomly-addressable indexed library file which can be interrogated by means of the HLP_HELP routine.
No facilities exist for inserting a single topic into an existing help library.